1. Field of the Invention
This invention refers to the production of halving-joints of arched frame portions made of wood for door arches, window arches, and the like, particularly semi-circular arches, portal arches, elliptical arches and the like of different diameters, and having-joint components for connecting such arches with each other.
2. Description of Prior Art
With curved door and window arches, it is necessary to mill the bevels of these arches, on the inner surface of the outer arch, on the outer and the inner surface of any middle arch, and on the outer surface of the inner arc. These bevels receive the radially extending, recessed straight struts and are symmetrically trapezoidal, to exact dimensions both as to width and height, and as to their location, in order to make sure that the straight strut portions, which extend perpendicular to the arches, fit exactly and snugly into the bevels. The arched frame portions, which are made from a plurality of laminated layers of wood, generally do not maintain their shape when being stored and handled, so that the bevels must be milled individually for obtaining the high degree of exactness necessary for a correct fit and an exact picture of the system of struts.
According to the state of the art, such bevels will be punched, sawn or cut manually sequentially, while the corresponding arched frame portion is clamped and the tool is adjusted manually to the location of the bevel to be machined, or vice versa. This is a rather complicated procedure, which takes quite a long time per bevel and which must be carried out by the operator with considerable attention and skill, if the plurality of bevels is to be made exactly. In those cases, in which the crossing angles between arches and associated struts are different from 90.degree., the struts at the crossing positions with the arches or alternatively the arches at the location of engagement with the struts necessarily are unsymmetrical in shape, which is caused by corresponding angles different from 90.degree.. According to the state of the art, the trapezoidal bevels Within the halving-joints and the straight struts are milled manually or by means of stencils, whereby the basic lines of the two opposite trapezoidal bevels of a strut are parallel to each other and extend in an acute angle to the longitudinal axis of the crossing strut. The strut of the bevels for elliptical arches is different from angle to angle so that for each required angle a different milling tool is required.